GLASS (Gr. ὑαλίνη) a generally transparent or translucent, lustrous, hard and brittle substance which has passed from a fluid condition, at high temperature, to a solid condition with sufficient rapidity to prevent the formation of visible crystals. Glass is formed in nature in three main ways. Rarely a silica glass is formed in small amounts when lightning strikes sand. The concentrated heat fuses the sand. The melt immediately solidifies forming a fragile tube of silica glass sometimes several ft. long. Such tubes are called fulgarites and are generally found in desert environments. Rarely, also, natural glass is formed as the result of localized melting of rock in a large fault zone, the glass generally being black and referred to as pseudotachylite. The most common natural occurrence of glass is as obsidian, a glassy volcanic rock of acidic composition used by early man for making small implements. Early sources of obsidian for countries of the Middle E were the Aegean region and Ethiopia. Later obsidian was obtained from Armenia and possibly from Lipari and Pentellera.
Manufactured glass consists primarily of a combination of silicic acid and alkali (sodium or potassium). Probably it originated somewhere in the eastern Mediterranean lands, possibly in Egypt, with the Egyptians making small glass-covered objects from about 4000 b.c. The first glass vessels appear to have been made c. 1500 b.c. In Egypt and in other coastlands, like Syria, soda glass was produced. This contains sodium and calcium silicates and is made by fusing white pure sand (silicon dioxide) free from iron compounds, soda-ash (sodium carbonate) and limestone (calcium carbonate) or lime (calcium oxide) in fireclay pots or tanks at 1375oC or above. The soda-ash was obtained from seaweed ash. Bohemian or potash glass contains potassium instead of sodium and was developed in well-wooded countries, particularly Germany, the potassium being derived from charcoal, particularly beech charcoal.
The ingredients of glass are rarely in a pure state, the sand generally containing some iron impurities. The green color they cause, due to ferrous silicate, may be neutralized by adding pyrolusite (manganese dioxide) (Gr. pyr “fire,” and luo “I wash”). The resultant glass may be clear and transparent (Rev 21:18) and look like still water (Rev 15:2). However, if there are numerous minute air bubbles left in the glass, it is translucent (Rev 21:21 NEB) and has the appearance of ice (Rev 4:6 NEB).
In modern times a mirror (cf. 2 Cor 3:18; James 1:23 NEB) is a sheet of polished glass silvered at the back. However, in ancient times it was a polished sheet of metal, called a speculum (cf. 1 Cor 13:12).
J. R. Partington. A Textbook of Inorganic Chemistry, 6th ed. (1950), 760, 761; J. McNab, “Glassware,” Collier’s Encyclopedia, 11 (1964), 143-152.
International Standard Bible Encyclopedia (1915)
Glass is of great antiquity. The story of its discovery by accident, as related by Pliny (NH, xxxvi.65), is apocryphal, but it was natural for the Greeks and Romans to ascribe it to the Phoenicians, since they were the producers of the article as known to them.
Phoenicia was the great center, and the quantities found in tombs of Syria and Palestine go to confirm the statement that this was one of the great industries of this people, to which ancient authors testify (Strabo, Geog.; Pliny, NH). Josephus refers to the sand of the Belus as that from which glass was made (BJ, II, x, 2). It seems to have been especially adapted for the purpose, but there are other places on the coast where plenty of suitable sand could be obtained. The potash required was obtained by burning certain marine and other plants, and saltpeter, or niter, was also employed. The manufacture began centuries BC on this coast, and in the 12th century AD a factory is mentioned as still being worked at Tyre, and the manufacture was later carried on at Hebron, even down to recent times (Perrot and Chipiez).
Both the Egyptians and Phoenicians gained such proficiency in making transparent and colored glass that they imitated precious stones with such skill as to deceive the unwary. Necklaces are found composed of a mixture of real brilliants and glass imitations. Cut glass was manufactured in Egypt as early as the XVIIIth Dynasty, and diamonds were made use of in the article Glass composed of different colors in the same piece was made by placing layers of glass wire, of different colors, one above the other and then fusing them so thar they became united in a solid mass without intermingling. Colored designs on the surface were produced by tracing the patterns, while the glass was still warm and plastic, deep enough to receive the threads of colored glass which were imbedded in them. The whole was heated again sufficiently to fuse the threads and attach them to the body. The surface was then made even by perishing. By this process vessels and ornaments of very beautiful design were produced. Many of the specimens, as found, are covered by an exquisite iridescence which is due wholly to the decomposition of the surface by chemical action, from lying buried for centuries in the soil which thus acts upon it. This is often lost in handling by the scaling off of the outer surface.
The composition of the Phoenician glass varies considerably. The analysis shows that, besides the ordinary constituents of silica, lime, lead, potash or soda, other elements are found, some being used for the purpose of coloring, such as manganese to give the purplish or violet hue, cobalt for blue, copper for red, etc. The articles illustrated above are of ordinary transparent glass with an iridescent surface, caused by decomposition, as mentioned above, indicated by the scaly appearance. Numbers 1, 4 and 5 are tear bottles, number 4 being only 1 3/4 inches in height; numbers 2 and 3 are ointment vases which were used for the ointment with which ladies were accustomed to color their eyebrows and eyelashes to enhance their beauty. This custom still prevails in the East. The small ladle by the side of the larger vase is of bronze, used in applying the ointment. This vase is double and 6 3/4 inches high, ornamented with glass wire wound upon it while plastic. The larger vases (numbers 6 and 7) are about 6 inches in height. The hand-mirror ("looking-glass" the King James Version) is bronze, and had originally a polished surface, but is now corroded.